CN110577659B - Preparation method of layered stacked photoluminescent ZIF-L film structure - Google Patents

Abstract

The invention discloses a preparation method of a layered stacked photoluminescent ZIF-L film structure, which comprises the following steps: mixing and dissolving zinc acetate dihydrate and 2-methylimidazole in a solvent to prepare ZIF-L sol; cleaning the thin film substrate; spin-coating ZIF-L sol on a substrate to form a film; the obtained wet film is thermally treated on a heating plate at the temperature of 60-80 ℃ for 1-3h, and then the temperature of the heating plate is slowly raised to 135-200 ℃ for heat preservation until the photoluminescence phenomenon appears. The ZIF-L film prepared by the invention has a two-dimensional layered compact stacking structure and has photoluminescence performance; the thickness and the crystallinity can be regulated and controlled by changing the concentration of the sol and the type of the substrate, so that the photoluminescence performance of the ZIF-L can be regulated and controlled; annealing treatment is carried out at different temperatures to regulate and control the photoluminescence color of the ZIF-L film to change from blue to orange red; low requirement on equipment, low cost, good film forming quality and good luminescence property.

Description

Preparation method of layered stacked photoluminescent ZIF-L film structure

Technical Field

The invention belongs to the technical field of materials, and particularly relates to a preparation method of a layered stacked photoluminescent ZIF-L film structure.

Background

Zeolitic Imidazolate Frameworks (ZIFs) are a branch of metal-organic frameworks (MOFs) which are composed of tetrahedral metal ion junctions and imidazole ligands. ZIF-L is a two-dimensional structure composed of metal ions Zn²⁺And 2-methylimidazole (Hmim), and has hierarchical morphology of leaf, rod and sheet, and the like, for CO²Has higher adsorption and selectivity, and meanwhile, ZIF-L has been used as an adsorbent to remove harmful substances such as dye, aromatic hydrocarbon, arsenic, heavy metal and the like, and can also be applied to the aspects of catalysts, drug delivery, sensors, gas storage and the like.

Regarding the preparation of ZIF-L, a zinc source generally adopted is zinc nitrate, and the preparation process of a ZIF-L film with good quality is generally complex, although the performance of ZIF-L materials is not studied at present, the study on adsorption, catalysis and other aspects of ZIF-L is more important, and the study on the photoluminescence phenomenon of a laminated tightly-stacked ZIF-L film is not seen at present.

Disclosure of Invention

The invention aims to provide a preparation method of a laminated and photoluminescent ZIF-L film structure, which is simple and has good film-forming quality, process repeatability and stability of the ZIF-L film.

In order to achieve the purpose, the technical scheme is as follows:

a preparation method of a layered stacked photoluminescent ZIF-L film structure comprises the following steps:

1) mixing and dissolving zinc acetate dihydrate and 2-methylimidazole in a solvent to prepare ZIF-L sol;

2) cleaning the thin film substrate;

3) spin-coating the ZIF-L sol obtained in the step (1) on the substrate obtained in the step (2) to form a film;

4) and (3) carrying out heat treatment on the wet film obtained in the step (3) on a heating plate at the temperature of 60-80 ℃ for 1-3h, and then slowly heating the heating plate to 135-200 ℃ and carrying out heat preservation until the photoluminescence phenomenon occurs.

According to the scheme, the molar ratio of the zinc acetate dihydrate to the 2-methylimidazole in the step 1 is 1 (1-2); the ratio of the 2-methylimidazole to the solvent is 0.025mol: 5-30 ml.

According to the scheme, the solvent in the step 1 is methanol or ethanol.

According to the scheme, zinc acetate dihydrate and 2-methylimidazole are mixed with a solvent in a molar ratio of 1:1-2 in the step 1, and the mixture is magnetically stirred at room temperature for at least 30min to obtain the colorless and transparent ZIF-L sol.

According to the scheme, the film substrate in the step 2 can be a common glass slide, sapphire or silicon chip and the like; the cleaning method comprises ultrasonic cleaning with deionized water and alcohol for 20-40 min.

According to the scheme, in the step 3, the substrate is placed on a spin coater platform, and the ZIF-L sol is uniformly coated on the substrate by a dropper for spin coating; the parameters in the spin coater are set as follows: the first step of rotating speed is 500-1000rp/min for 5-10s, and the second step of rotating speed is 3000-3500rp/min for 15-20s, thus obtaining the transparent ZIF-L wet film.

According to the scheme, the method further comprises the following steps:

and (4) keeping the temperature rise rate of the ZIF-L film obtained in the step (4) at 5-10 ℃/min and keeping the temperature at 300 ℃ for 1h at 240 ℃ and annealing treatment, wherein the film shows the change of different photoluminescence colors.

Compared with the prior art, the technical scheme of the invention has the following beneficial effects:

(1) the ZIF-L film prepared by the method has a two-dimensional layered compact stack structure and has photoluminescence performance;

(2) the thickness and the crystallinity of the ZIF-L film can be regulated and controlled by changing the volume of a solvent methanol (or ethanol), namely the concentration of sol and the type of a substrate, so that the photoluminescence performance of the ZIF-L can be regulated and controlled;

(3) annealing the cured ZIF-L film at different temperatures to regulate the photoluminescence color of the ZIF-L film to change from blue to orange red;

(4) the ZIF-L film prepared by the method has the advantages of good repeatability and stability, low equipment requirement, low cost, good film forming quality and good luminescence property.

Drawings

FIG. 1: example 1 XRD pattern of ZIF-L film prepared by spin-coating sol on sapphire substrate;

FIG. 2: FESEM image of ZIF-L film in example 1;

FIG. 3: PL spectrum of ZIF-L film in example 1 excited by light having wavelength of 365 nm;

FIG. 4: example 2XRD pattern of ZIF-L film prepared by spin-coating sol on a common glass slide substrate;

FIG. 5: FESEM image of ZIF-L film in example 2;

FIG. 6: PL profile of ZIF-L film in example 2 upon excitation with 365nm wavelength light.

Detailed Description

Other aspects, features and advantages of the present invention will become apparent from the following detailed description, which, when taken in conjunction with the drawings, illustrate by way of example the principles of the invention.

Example 1

(1) Preparing ZIF-L sol (the molar ratio of reactants is 1:1, and the ratio of 2-methylimidazole to solvent is 0.025mol:5 ml): 5.4878g of zinc acetate dihydrate and 2.0525g of 2-methylimidazole are respectively weighed and placed in a small glass bottle filled with magnetons, 5ml of methanol is added into the glass bottle, the glass bottle is placed on a magnetic stirrer to be mixed and stirred for 30min, and the 5mol/L ZIF-L sol is obtained.

(2) Cleaning of the thin film substrate: in order to avoid the influence of weak luminescence of the substrate on the photoluminescence performance of the ZIF-L film, the substrate adopted by the invention is sapphire. The specific cleaning step is to sequentially use deionized water and alcohol solution to carry out ultrasonic treatment on the sapphire for 20 min.

(3) Spin coating a film on the substrate: and (3) placing the sapphire substrate on a spin coater platform, uniformly coating the ZIF-L sol on the substrate by using a dropper, and setting parameters for uniform coating. The parameters are set as follows: the first step is carried out at a rotating speed of 500rp/min for 10s, the second step is carried out at a rotating speed of 3500rp/min for 15s, and the ZIF-L wet film is obtained after one-time spin coating.

(4) Heat treatment of the spin-coated ZIF-L wet film: and (3) carrying out heat treatment on the ZIF-L wet film on a heating plate at the temperature of 80 ℃ for 1h, and then slowly heating the heating plate to the temperature of 135 ℃ and carrying out heat preservation until a photoluminescence phenomenon appears.

Referring to FIGS. 1, 2 and 3, which show the characteristics of film sample 1, FIG. 1 is an XRD pattern of ZIF-L in example 1, and the crystallinity is good as indicated by sharp peak shape. FIG. 2 is an FESEM image of ZIF-L of example 1, showing that there is a significant two-dimensional lamellar stacking structure on the surface of the film, and that the film thickness is about 6.56 μm and there is significant stacking of the lamellar structure as seen from the cross-sectional scan, illustrating the two-dimensional lamellar structure of ZIF-L. FIG. 3 is an emission spectrum obtained by 365nm light excitation, which shows that the emission wavelength range is 400-500nm, and mainly emits blue light. The prepared ZIF-L film has good film forming quality and stable luminescence property, and is expected to be applied to photoluminescent thin film devices.

Example 2

(1) Preparing ZIF-L sol (the molar ratio of reactants is 1:2, and the ratio of 2-methylimidazole to solvent is 0.050mol:30 ml): 5.4878g of zinc acetate dihydrate and 4.1050g of 2-methylimidazole are respectively weighed and placed in a small glass bottle filled with magnetons, 15ml of methanol is added into the glass bottle, the glass bottle is placed on a magnetic stirrer to be mixed and stirred for 60min, and the ZIF-L sol with the concentration of 1.67mol/L is obtained.

(2) Cleaning of the thin film substrate: in order to avoid the influence of weak luminescence of the substrate on the photoluminescence performance of the ZIF-L film, the substrate adopted by the invention is a standard grade glass slide. The specific cleaning step is to sequentially use deionized water and alcohol solution to carry out ultrasonic treatment on the glass slide for 40 min.

(3) Spin coating a film on the substrate: and (3) placing the glass slide substrate on a spin coater platform, uniformly coating the ZIF-L sol on the substrate by using a dropper, and setting parameters for uniform coating. The parameters are set as follows: the first step is carried out at the rotating speed of 1000rp/min for 5s, the second step is carried out at the rotating speed of 3000rp/min for 20s, and the ZIF-L wet film is obtained after one-time spin coating.

(4) Heat treatment of the spin-coated ZIF-L wet film: and (3) carrying out heat treatment on the ZIF-L wet film on a heating plate at 60 ℃ for 3h, and then slowly heating the heating plate to 200 ℃ and carrying out heat preservation until a photoluminescence phenomenon appears.

(5) And (4) placing the ZIF-L film cured in the step (4) into an annealing furnace for annealing treatment, setting the program to be 5 ℃/min to raise the temperature to 260 ℃, and then preserving the heat for 1h to finish the program.

FIG. 4 is an XRD pattern of a thin film sample obtained in example 2, and compared with the XRD pattern of FIG. 2 in example 1, the peak position is unchanged but only a very wide peak packet exists, and it is possible that the amorphous phase in the thin film occupies a large portion, indicating that the concentration of the spin-on sol and the kind of the substrate affect the structure of the ZIF-L thin film to some extent. FIG. 5 is an FESEM image of a ZIF-L film of example 2, which has a uniform surface with no significant sheet-like structures, and which has a measured film thickness of about 1.80 μm, and which has sheet-like structures growing vertically to the substrate surface at the edges of the film cross-section, indicating that the film has short-range order, long-range disorder, and weak crystallinity. FIG. 6 is an emission spectrum measured by 365nm wavelength light excitation, from which it can be seen that the emission peak is very broad, the emission wavelength is about 400-650nm, and the main yellow-green light is observed by naked eyes. Because the luminescent properties of the films prepared by spin coating the ZIF-L sol with different concentrations are different, and the luminescent colors of the films obtained by carrying out heat treatment on the films at different temperatures are different, the film devices emitting different colors can be prepared according to actual requirements.

The ZIF-L film structure prepared by the invention has a compact stacking phenomenon of a laminated structure and has photoluminescence performance. The control of the ZIF-L crystallinity, film thickness and photoluminescence color can be realized by properly controlling the concentration of the ZIF-L sol, the curing conditions, the annealing temperature and other process parameters. The ZIF-L film prepared by the method has the advantages of simple process, uniform and controllable film formation, stable photoluminescence performance and repeated preparation.

The raw materials listed in the invention, the upper and lower limits and interval values of the raw materials of the invention, and the upper and lower limits and interval values of the process parameters (such as temperature, time and the like) can all realize the invention, and the examples are not listed.

While the foregoing is directed to the preferred embodiment of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.

Claims (5)

1. A preparation method of a layered stacked photoluminescent ZIF-L film structure is characterized by comprising the following steps:

1) mixing and dissolving zinc acetate dihydrate and 2-methylimidazole in a solvent, and magnetically stirring at room temperature for at least 30min to obtain colorless and transparent ZIF-L sol; the molar ratio of the zinc acetate dihydrate to the 2-methylimidazole is 1 (1-2); the ratio of the 2-methylimidazole to the solvent is 0.025mol: 5-30 ml;

2) cleaning the thin film substrate;

3) spin-coating the ZIF-L sol obtained in the step (1) on the substrate obtained in the step (2) to form a film;

4) and (3) carrying out heat treatment on the wet film obtained in the step (3) on a heating plate at the temperature of 60-80 ℃ for 1-3h, and then slowly heating the heating plate to 135-200 ℃ and carrying out heat preservation until the photoluminescence phenomenon occurs.

2. The method of fabricating a layered stacked photoluminescent ZIF-L film structure of claim 1, wherein the solvent in step 1 is methanol or ethanol.

3. The method for preparing a layered stacked photoluminescent ZIF-L film structure of claim 1, wherein the thin film substrate in step 2 is a common glass slide, sapphire, or silicon wafer; the cleaning method comprises ultrasonic cleaning with deionized water and alcohol for 20-40 min.

4. The method for preparing a layered stacked photoluminescent ZIF-L film structure of claim 1, wherein in step 3, the substrate is placed on a spin coater platform, and the ZIF-L sol is uniformly coated on the substrate by a dropper for spin coating; the parameters in the spin coater are set as follows: the first step of rotating speed is 500-1000rp/min for 5-10s, and the second step of rotating speed is 3000-3500rp/min for 15-20s, thus obtaining the transparent ZIF-L wet film.

5. The method of fabricating a layered-stacked photoluminescent ZIF-L film structure of claim 1, further comprising an annealing process:

and (4) keeping the temperature rise rate of the ZIF-L film obtained in the step (4) at 5-10 ℃/min and keeping the temperature at 300 ℃ for 1h at 240 ℃ and annealing treatment, wherein the film shows the change of different photoluminescence colors.

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